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Depozice tenkých vrstev Ba.sub.x./sub.Sr.sub.1-x./sub.TiO.sub.3./sub. pomocí dvoutryskového RF plazmatického systému s efektem duté katody
Hubička, Zdeněk ; Virostko, Petr ; Olejníček, Jiří ; Deyneka, Alexander ; Adámek, Petr ; Valvoda, V. ; Jastrabík, Lubomír ; Šícha, Miloš ; Tichý, M.
Low-pressure plasma jet system with two hollow cathodes was used for deposition of BaxSr1-xTiO3 (BSTO) ferroelectric thin films. High density pulse modulated RF hollow cathode discharge was generated in ceramic nozzles made of SrTiO3 and BaTiO3. In the experiment, the composition of BSTO films was controlled by magnitude of average RF power applied on particular plasma jet guns. X-ray diffraction proved that BSTO thin films were polycrystalline with perovskite structure. Time resolved Langmuir probe system and plasma impedance monitor were used for ´in situ´ plasma diagnostics and control of deposition conditions.
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Vliv připojeni oblouku k anodě na proud termického plazmatu
Chumak, Oleksiy ; Kavka, Tetyana ; Hrabovský, Milan
The paper examines an effect of an argon amount on the thermal plasma jet generated from water/argon mixture in a dc arc plasma torch. In spite of an increase of plasma velocity with an addition of argon a decrease of plasma jet length is observed for bigger argon amount in the plasma. The investigation was based on an analysis of a jet structure based on imaging of the plasma jet by a CCD camera. Statistical processing of plasma jet photographs provided information about a jet shape and its fluctuations space distribution. It was found that an argon amount increase caused significant intensification of the plasma jet fluctuations.
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Měření excitačních a ionizačních teplot v expandujícím proudu H2O-Ar plazmatu
Sember, Viktor ; Mašláni, Alan
Optical emission spectroscopy is used to determine the temperature in a plasma jet expanding from the H2O-Ar dc arc torch into a chamber maintained at a pressure of 10 kPa. The excitation and rotational temperatures are derived from relative intensities of argon atomic and ionic lines, and from the UV OH band at 306.357 nm, respectively. The ionization temperature is obtained from the intensity ratio of argon ionic and atomic lines, using electron number density calculated from the Stark broadening of hydrogen H line. The structure of the plasma jet is characterized by isocontours of electron number density and intensity of atomic and ionic lines. In the expansion region, the ionic excitation temperature is found close to the ionization temperature and much higher than the excitation temperature of argon atoms, which is close to the rotational temperature of OH radical. In the normal shock region, all the measured temperatures tend to be equal.
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Statistické zpracovani obrázku plazmatického prouděni pro vizualizace nestabilit
Chumak, Oleksiy
The structure and stability of a thermal plasma jet were studied on the basis of statistical analysis of images of a plasma jet taken by a fast shutter camera. The space distribution of the mean value and the standard deviation of image brightness were evaluated from a sequence of images. The short exposure time ensured imaging of the momentary state of the jet while analysis of a sequence of images provided information about jet fluctuations. Effect of arc current was investigated. Arc power increase led to higher fluctuations of the jet, although it caused increase of the jet length.
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Nové metody záznamu chování volného proudu plazmatu užívající vláknovou optiku
Šonský, Jiří ; Hlína, Jan ; Něnička, Václav
The fibre optics coupling to photodiodes used in plasma jets optical radiation recording enables us to increase the channel count and to add flexibility to an experimental layout for multi-directional observations. These improvements give us opportunity of more detailed and important plasma jets behaviour analysis - reconstruction of luminosity fields (close to relative value of enthalpy) in planes perpendicular to a plasma jet axis, velocities and tracking of plasma jet axis movements. Details of experimental hardware and layount will be also shortly presented.
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Modelování směšování plazmatu vodní páry s parní atmosférou v tepelném plazmovém reaktoru
Hirka, Ivan ; Jeništa, Jiří ; Hrabovský, Milan
Two-dimensional CFD modelling of mixing of steam plasma jet with steam atmosphere in thermal plasma reactor has been carried out. Temperature of steam plasma is approximately 15 000 K and temperature of steam atmosphere is 400 K. Standard, RNG, and realizable k-e models were used for all simulations. Steam plasma and steam atmospheric properties were generated by the ADEP code. Results for temperature, velocity and density distributions are discussed and presented as images obtained from the FLUENT code, for currently used reactor geometry setup and plasma flow.
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Identifikace vírových struktur z experimentálních dat
Šonský, Jiří ; Něnička, Václav ; Jágerská, J.
For identification of vortex structures of a heat flow in a free burning plasma jet a new method is used, which utilize fast imaging methods and computerized image processing. This method allows us to observe genesis of vortexes of a heat flow in a plasma jet, including the changes when a wall barrier is inserted in the jet. These two regimes are typical for behaviour of a plasma jet in technological applications. By varying the flow rate of working gas (argon, 15slm to 150 slm) there appear considerable changes both in time and spatial distribution of vortex fields in the two above regimes
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